1. Field of the Invention
The present invention relates to a sample data transmitting method, a sample data receiving method, and a sample data transmission method as well as its transmitting apparatus, its receiving apparatus, and its transmission apparatus suited for use to reproduce DVD audio to which is applied, for example, DVD-ROM (Read-Only-Memory). Particularly, it is intended that a plurality of data sampled at different sampling frequencies can effectively be transmitted in a predetermined transmission format.
2. Description of the Related Art
For example, as a recording medium of a digitized sound signal, a DVD audio to which DVD-ROM is applied has been developed. Then, in such DVD audio, by taking advantage of the fact that a recording capacity of the DVD-ROM is extremely large, an attempt has been carried out to record a multi-channel and high quality sound signal with a sampling frequency set at 96 kHz for example.
Specifically, as for a format of such DVD audio, a total of four channels are recorded by providing 2 channels of sample data for example, with a sampling frequency of 96 kHz and the number of quantized bits of 24 bits for a main acoustic signal as well as 2 channels of sample data with a sampling frequency of 48 kHz and the number of quantized bits of 16 bits for a sub-acoustic signal such as a so-called surround and the like.
By the way, with a digital acoustic apparatus such as a DVD player and the like, the conventional one has been made for example, to D/A-convert a digitally reproduced signal within the apparatus to take out as an analog acoustic signal and supply it to another amplifier and the like. However, an originally digitized signal is advantageously transmitted as it is against signal deterioration during transmission. Also, for example, by using busfrom transmission paths, the number of laid-on transmission paths can be reduced.
Then, as a means for transmitting such a digital acoustic signal as it is, a format regulated by IEEE1394 is used for example. According to the format, a synchronizing signal (cycle start) is generated from, for example, reference apparatus as a constant cycle (125 xcexcs) as shown in FIG. 1. Between the synchronized signals, an arbitrary number of signal channels (1 to n) called isochronous (synchronous) packet are provided.
The isochronous packet has a structure, e.g. as shown in FIG. 2A. The first row of the packet is one quadlet (4 bites=32 bits). For the first half 2 bytes in the first row of the packet -is provided a value (data length) indicating a length of the subsequent area. Also, for the latter half 2 bytes in the first row are provided a value (tag) showing a format of the packet, a value (channel) showing a channel number, a value (tcode) to identify the packet, a value (sy) used for synchronization and so on.
That is, the first row of the isochronous packet is made a header area wherein information on various kinds of controls is provided. Further, in the second row is provided an error correcting code (header CRC) for data on the above-mentioned header area in the first row. Then, in and after the third row of the isochronous packet is provided data on a digital acoustic signal to be transmitted and the like over the range shown in the above-mentioned value (data length). Also, in the last row of the packet is provided an error correcting code (data CRC) for data transmitted in and after the third row.
Moreover, a section for transmitting such as control information and the like called an asynchronous (nonsynchronous) packet is provided in a remaining period after the isochronous packet (the minimum amount is secured) between on the above synchronizing signals (cycle start). Then, in accordance with control information transmitted via the asynchronous packet, transmission of the digital acoustic signal and the like is carried out between arbitrary apparatuses using some channel of the above-mentioned asynchronous packet.
In FIG. 2B is shown a structure of the asynchronous packet where controlling information (data) of, for example, one quadlet is written into a desired memory or register of the arbitrary apparatus. The first row of the packet is one quadlet and for the first half 2 bytes in the first row is provided an identifying code of a destination (addressee) apparatus (destination ID). Also, for the first half 2 bytes in the second row is provided an identifying code of a sending apparatus (source ID). Meanwhile, these identifying codes are beforehand set for each of apparatuses for example, at a time of constructing a system.
For the latter half 2 bytes in the first row are provided a label (t1) for showing a series of controlled states (transaction), a code (rt) for showing a status of retransmission, a value (tcode) for distinguishing the packet and a value (pri) for showing order of priority. Further, for the latter half 2 bytes in the second row and in the third row are provided addresses of a memory of the destination and the like (destination offset). Data of 4 bytes to be written is provided in the fourth row. Then, in the fifth row is provided error correcting codes (header CRC) for each of data in the first to fourth rows.
Furthermore, in FIG. 2C is shown a structure of the synchronizing signal (cycle start). The synchronizing signal is also transmitted with the structure of the asynchronous packet. The first and third rows of this packet are the same as those of another asynchronous packet. However, with the packet of synchronizing signal, all apparatuses are designated by the destination identifying code in the first half 2 bytes in the first row. The sender identifying code of the first half 2 bytes in the second row provides that of the reference apparatus.
In the fourth row of the packet is provided a cycle time code (a value of a timer register provided in the reference apparatus). Further, in the fifth row is provided an error correcting code (header CRC) for each of data in the first to fourth rows. By the way, in the asynchronous packet are defined some forms other than this such as a writing, a read-out request and a read-out response for data of 1 quadlet or more but they are not relevant to this application and thus are not described.
Therefore, by using such a transmission format, it is possible for a bus line to connect between, for example, the above-mentioned DVD player or the like and the acoustic apparatus of other digital formats or the like. Thus, mutual control is carried out between these apparatuses using the control information transmitted by way of the above-mentioned asynchronous packet. This control enables mutual transmission of data such as an arbitrary digital acoustic signal and the like by using some channel of the above-mentioned asynchronous packet between these apparatuses.
However, in such a transmission format, for example, a sampling frequency of a digital acoustic signal is such that one frequency is determined corresponding to a signal of one system. Therefore, when there are a main acoustic signal at, a sampling frequency of 96 kHz and a sub-acoustic signal at a sampling frequency of 48 kHz as the above-mentioned DVD audio recording signal, it has been impossible to transmit these signals collectively (en bloc) on the conventional format.
Then, when these signals are transmitted on the conventional format, it is conceivable that the sub-acoustic signal at a sampling frequency of 48 kHz is doubled by a prior value holding or the like and is transmitted twice at a timing rate of the sampling frequency of 96 kHz. However, with this method, data to be transmitted becomes redundant with a resultant degradation in data transmission efficiency by the whole bus. It is also conceivable that the system is divided according to, for example, sampling frequency, but there then arises a necessity to provide a reproducing means for each system, and also a necessity to maintain synchronization among respective systems, which makes an apparatus complicated.
The present invention is implemented in view of these points and the problems to be solved are such that the conventional transmission format has made it impossible to transmit signals sampled at different sampling frequencies en bloc and when such signals are to be transmitted, there has been a fear that data transmission efficiency is degraded and the apparatus becomes complicated.
Therefore, the present invention is such that, for sample data at different sampling frequencies, data generated during one of the sampling periods is collected together to form a data block and at the same time, data of the number of sample data generated during the sampling period is added thereto. This makes it possible to transmit en bloc signals at different sampling frequencies as well as to easily reconstruct and restore these sample data.